Final answer:
Smallpox is primarily an airborne disease transmitted through the inhalation of viral particles, but it can also spread through direct contact. Though eradicated, understanding its transmission is vital for bioterrorism preparedness.
Step-by-step explanation:
The mode of transmission for Smallpox is generally airborne, specifically through the inhalation of viral particles shed from lesions in the throat of an infected individual. Once inhaled, the virus spreads systemically through the bloodstream and manifests as a pustular skin rash. The transmission can also occur via direct contact with infected bodily fluids or contaminated objects. Notably, Smallpox has been eradicated due to a global vaccination campaign led by the World Health Organization. However, knowledge about Smallpox, including its transmission, remains crucial in the event of a bioterrorism threat, as laboratory samples of the virus still exist.